Chevrolet Corvette 1963 Repair & Tune-Up Manual page 328

298 TROUBLESHOOTING
BEFORE SHORT CIRCUIT
AFTER SHORT CIRCUIT
Most fusible .links show a charred, melted Insula-
tion when they burn out
chassis electrical components, and is the
probable cause of trouble when none of the
electrical components function, unless the
battery is disconnected or dead.
Electrical problems generally fall into one
of three areas:
1. The component that is not functioning
is not receiving current.
2. The component itself is not functioning.
3. The component is not properly ground
ed.
The electrical system can be checked with
a test light and a jumper wire. A test light is a
device that looks like a pointed screwdriver
with a wire attached to it and has a light bulb
in its handle. A jumper wire is a piece of
insulated wire with an alligator clip attached
to each end.
If a component is not working, you must
follow a systematic plan to determine which
of the three causes is the villain.
1. Turn on the switch that controls the in
operable component.
2. Disconnect the power supply wire from
the component,
3. Attach the ground wire on the test light
to a good metal ground.
4. Touch the probe end of the test light to
the end of the power supply wire that was
disconnected from the component. If the
component is receiving current, the test light
will go on.
NOTE: Some components work only when
the ignition switch is turned on.
If the test light does not go on, then the
problem is in the circuit between the battery
and the component. This includes all the
switches, fuses, and relays in the system.
Follow the wire that runs back to the battery.
The problem is an open circuit between the
COVERING BUBBLED
AND CHARRED
WIRE BURNED
OPEN
The test light will show the presence of current
when touched to a hot wire and grounded at the
other end
battery and the component. If the fuse is
blown and, when replaced, immediately
blows again, there is a short circuit in the sys-
tem which must be located and repaired. If
there is a switch in the system, bypass it with
a jumper wire. This is done by connecting
one end of the jumper wire to the power
supply wire into the switch and the other end
of the jumper wire to the wire coming out'of
the switch. If the test light lights with the
jumper wire installed, the switch or what-
ever was bypassed is defective.
NOTE: Never substitute the jumper wire
for the component, since it is required to use
the power from the power source.
5. If the bulb in the test light goes on,
then the current is getting to the component
that is not working. This eliminates the first
of the three possible causes. Connect the
power supply wire and connect a jumper
wire from the component to a good metal
ground. Do this with the switch which con
trols the component turned on, and also the
ignition switch turned on if it is required for
the component to work. If the component
works with the jumper wire installed, then it
has a bad ground. This is usually caused by
the metal area on which the component
mounts to the chassis being coated with
some type of foreign matter.
6. If neither test located the source of the
trouble, then the component itself is defec
tive. Remember that for any electrical sys
tem to work, all connections must be clean
and tight.